A repeater was developed to improve the call quality in mobile communication and overcome a communication blind zone, and has been installed over various areas. The repeater provides a communication service to areas blocked or isolated from the outside, by filtering and amplifying signals depending on different frequency bands.
For example, in Korea, frequencies are allocated in a unit of 10 MHz to communication service providers. Seven (7) frequency channels are operated within an allocated frequency band. For example, if a communication service provider A uses a band of 20 MHz, and a communication service provider B uses a band of 10 MHz, a mobile communication repeater has a standard to execute filtering depending on the different frequency bands.
Korean Patent Application Publication No. 10-2009-0110669 (title of the invention: Repeater Variable Gain Ripple Compensation Circuit, Repeater Variable Gain Ripple Compensation Apparatus, and Method Thereof) describes a repeater configured by a ripple compensation circuit using an analog method in adjusting a frequency, the number of channels, and a bandwidth. If the ripple compensation circuit is used, it is necessary to manufacture a repeater having a fixed frequency, the fixed number of channels, and a fixed bandwidth. Thus, if a frequency band in a place or an area where the repeater is installed is changed, the repeater needs to be replaced or an inner circuit of the repeater needs to be constructed again.
In order to avoid the unnecessary works, a repeater capable of adjusting a frequency, the number of channels, and a bandwidth by adding a compensation circuit has been manufactured. However, since an analog circuit is added, the volume of the repeater and manufacturing costs thereof increase. Thus, there has been a difficulty in effectively constructing a repeater.
In order to solve the problems of the increase in volume and manufacturing costs caused by the change in the inner circuit of the repeater, Korean Patent No. 10-0892619 (title of the invention: Digital Filter Apparatus of Mobile Communication Repeater Channel Frequency Using Time-Division Filtering Method) describes a repeater, in which a ripple compensation circuit is replaced with a digital filter. However, the repeater using the digital filter is embodied in the manner that fixed frequency information, information of the fixed number of channels, and fixed bandwidth information are pre-stored in a memory of a digital board and taken therefrom. Since the information should be pre-stored in the memory of the digital board, if a multiple number of communication service providers operate frequency channels with different frequencies, different numbers of channels, and different bandwidths depending on areas, it is necessary to develop a multiple number of equipments suitable for frequency characteristics of the respective communication service providers.